This invention relates to oxidation of alkanes using metalloporphyrins as catalysts, and more particularly to such processes in which cyano groups have been substituted for hydrogen in the porphyrin ligand.
The use of metalloporphyrins as catalysts for the oxidation of hydrocarbons with air in the liquid phase has been shown by the inventors in U.S. Pat. Nos. 4,895,680 and 4,895,682 with the further finding that halogenation of the porphyrin ring led to even more active and stable catalysts (U.S. Pat. Nos. 4,900,871, 4,970,348 and U.S. patent application Ser. No. 568,118). Since these discoveries we have been able to correlate increased electron withdrawal from halogenation of the porphyrin ring to increased catalytic air oxidation activity. J. E. Lyons and P. E. Ellis, Jr., Catalysis Letters, 8, 45 (1991).
Other functional groups besides halogens can lead to increased electron withdrawal from the metal center in metalloporphyrins. For example, cyano groups are known for their large electron withdrawing inductive effects and cyano containing metalloporphyrins with cyano groups in the beta or pyrrolic positions have been shown to be more easily reduced than their precursors without cyano substitution. R. J. Donohoe, M. Atamian and D. F. Bocian, J. Amer. Chem. Soc., 109, 5593 (1987).